Propeller initialization pulse waveforms

Vega256

Hey guys,

It is to my understanding that Propeller pins 37...40 (Comm pins 28...31) are used for program loading during initialization of the Propeller. Can anyone tell me the waveforms of the pulses emitted from these pins? Can they be used as freely as other comm pins after boot-up?

Paul

I've never measured them but I would assume they are a digital pulse train during start up. They can be used as common I/O after start up but remember the EEPROM pins, 37,38 probably have pull-up resistors. Please check the spec sheet to be sure.

Mike Green

Once the Prop has loaded a program and the program starts executing, I/O pins 28..31 are no longer used and could be used for other purposes. That said, their use has to take into account what's connected to those pins for initialization purposes.

1) I/O pins 28 and 29 are used for the I2C EEPROM. During initialization, the signals on those pins are standard I2C protocol. This is well documented in the EEPROM datasheet.

2) I/O pins 30 and 31 are used for ordinary asynchronous I/O with a PC. I/O pin 30 is used to transmit to the PC and I/O pin 31 is used to receive from the PC. There's a description of the download protocol available.

Generally, I/O pins 28 and 29 are used for additional I2C devices. If you do this, make sure to add a pull-up (like 4.7K to Vdd) on SCL (pin 28) if there's not one already there.